Sex determination

Després d’una descripció del que és el sexe, quan va aparèixer i per a què serveix, malgrat els seus costos, es descriuen els principals tipus de mecanismes de determinació del sexe tot centrant-nos en el que succeeix als vertebrats. Aquests mecanismes, en conjunt, es poden classificar com a genètics i ambientals, tot i que avui es tendeix a desdibuixar la seva separació. Entre els primers, s’inclou la determinació del sexe per factors (gens) “màster” o principals, com passa als mamífers, i sistemes multi- i poligènics, com passa en alguns peixos. Es descriuen també els gens determinants del sexe coneguts fins ara i perquè la seva diversitat constitueix una de les grans paradoxes dins de la biologia del desenvolupament. Seguidament, es parla de la determinació del sexe per factors ambientals, notablement la temperatura, i com l’epigenètica s’ha erigit en un disciplina ideal per estudiar la integració de la informació genètica i ambiental per a donar lloc a un fenotip sexual determinat. A continuació, es descriu el procés de diferenciació sexual i com els estrògens hi tenen una importància cabdal en tots els vertebrats excepte els mamífers placentats. Finalment, es mencionen les aplicacions de l’estudi de la determinació del sexe. Aquestes inclouen la diagnosi i comprensió dels trastorns del desenvolupament sexual en humans, el control de la proporció de sexes en la producció animal, particularment l’aquàtica, pel major creixement d’un sexe respecte l’altre, i els efectes que la pol·lució i el canvi climàtic poden tenir o ja tenen en la determinació del sexe als vertebrats.After a description of what sex is, when it appeared and the purpose it serves despite its costs, the main types of sex-determining mechanisms are described, focusing on the situation in vertebrates. These mechanisms can broadly be classified as genetic and environmental, although today there is a tendency to blur this separation. The genetic mechanisms include the determination of sex by main factors or “master” genes, as in mammals, and multi-and polygenic systems, as in some fish. We describe the sex genes known to date and explain why their diversity is one of the great paradoxes in development biology. Next, we present the determination of sex by environmental factors, particularly by temperature, and explain why epigenetics is emerging as an ideal discipline for studying the integration of genetic and environmental information to give rise to a given sexual phenotype. We then describe the process of sexual differentiation and how estrogens are of paramount importance for ovarian differentiation in all vertebrates except placental mammals. Finally, the applications of studying sex determination are mentioned. These include the diagnosis and understanding of sexual development disorders in humans, controlling sex ratios in animal production—particularly in aquatic animals due to the greater growth of one sex than the other—and the effects that pollution and climate change may have, or already have, in the determination of sex in some vertebrates

Què saben i què han après les estudiants de mestra de primària per ensenyar ciències socials? : un estudi de cas sobre la formació inicial en Didàctica de les Ciències Socials a Blanquerna - URL /

Consultable des del TDXTítol obtingut de la portada digitalitzadaAquesta investigació descriu, analitza i valora els aprenentatges realitzats per tres estudiants de 3r curs de Magisteri de l'especialitat d'Educació Primària per ensenyar ciències socials. Intenta esbrinar quin és l'impacte del programa de Didàctica de les Ciències Socials i del Pràcticum de la seva formació inicial, per capacitar-les per ensenyar l'àrea de Coneixement del Medi Social i Cultural de Primària. Per això s'analitzen primer les representacions prèvies que tenen aquestes estudiants de les ciències socials i del seu ensenyament-aprenentatge i es detecten en començar el curs coneixements i habilitats necessàries per ensenyar aquesta matèria. Aquestes representacions i coneixements inicials són contrastats amb les representacions i coneixements finals, per analitzar-ne els canvis i els aprenentatges realitzats. La majoria d'alumnes parteixen d'una experiència poc innovadora de l'ensenyament i l'aprenentatge de les ciències socials. Per aquest motiu, la investigació es planteja com a objectiu identificar els factors de la relació entre la teoria i la pràctica (tant a la facultat com a l'escola), que afavoreixen i dificulten el canvi conceptual i de la pràctica de l'ensenyament d'aquesta àrea, per introduir un model curricular més crític i constructivista. La metodologia aplicada ha estat la d'un estudi de cas, en la qual s'ha fet el seguiment durant tot un curs de les tres alumnes que han cursat simultàniament les assignatures de Didàctica de les Ciències Socials i de Pràcticum, impartides en els dos casos pel mateix professor, que ha estat alhora l'autor d'aquesta recerca. La investigació presenta i justifica els programes impartits en aquestes dues assignatures i descriu els continguts treballats i les activitats d'aprenentatge i d'avaluació realitzades en les diverses sessions del curs. En el treball de camp s'han triangulat tres tipus d'instruments per a l'obtenció d'informació sobre els seus aprenentatges : les entrevistes, les observacions directes i la producció escrita. S'han realitzat diverses entrevistes al llarg del curs (quatre a cada alumna i tres més a cada mestra-tutora, que era la responsable d'impartir l'àrea de Coneixement del Medi Social i Cultural a l'aula de pràctiques). Durant l'estada intensiva de pràctiques (mes de febrer), les alumnes han impartit una unitat didàctica d'aquesta àrea. Els temes realitzats han estat «Les comarques de Catalunya», a 4t, «La indústria tèxtil», també a 4t, i «La Unió Europea», a 6è. Les memòries de les pràctiques exposen i analitzen la preparació, realització i avaluació d'aquestes sessions, algunes de les quals han estat observades directament per l'investigador. La producció escrita és la que ha aplegat el volum més gran d'informació, entre les activitats d'avaluació inicial, els diversos exercicis realitzats a l'aula, els treballs individuals, els exàmens, els informes de pràctiques... En la interpretació final de la informació obtinguda en cada cas, s'han analitzat sis variables del procés formatiu : les pròpies practicants, les mestres de les escoles, els grups d'alumnes de primària, els contextos de la pràctica (disponibilitat d'espai, temps, materials...), el tutor de pràctiques de la facultat i el professor de l'assignatura de Didàctica de les Ciències Socials. Les conclusions evidencien algunes coincidències en les dificultats trobades per les tres alumnes a l'hora de racionalitzar i canviar les seves concepcions i les seves pràctiques per ensenyar ciències socials. La tesi apunta les modificacions que caldria introduir en el propi programa de l'assignatura però també en el Pràcticum i en el conjunt de l'actual pla d'estudis de Magisteri, perquè estudiants i professors disposin d'unes condicions més favorables per construir junts i de forma més significativa, un model d'ensenyament de les Ciències Socials més innovador.This research describes, analyses and assesses the learning process carried out by three Primary Education preservice teachers in their third year of Teacher Training studies to teach social studies. The aim is to find out what impact the Social Studies Methods course and Practicum in their initial training have, to enable them to teach the area of Knowledge of Social and Cultural Environment in Primary. To do so, we first analyze the previous representations that these preservice teachers have about social studies and their teaching-learning, and at the beginning of their third academic year their knowledge and skills to teach this subject are detected. These initial representations and knowledge are contrasted with their final representations and knowledge, in order to analyze changes and learning. Most preservice teachers share a background of scarcely innovating teaching-learning experience of social studies. For this reason, this research has the aim of identifying the relational factors between theory and practice (both at the Faculty and at the school) that enhance and inhibit the conceptual and teaching practice change in this area, to introduce a more critical and constructivist curricular model. The method used is that of a case study, where the three preservice teachers have been followed up for the whole academic year, in their subjects of Social Studies Methods and Practicum, given by the same teacher and author of this research. This research presents and justifies the syllabus given in these two subjects, and describes the contents and learning and assessing activities carried out in the different sessions of the course. In the field work, three kinds of instruments have been used to collect information about their learning: interviews, direct observations, and written reports. Throughout the course, different interviews were carried out (four with each preservice teacher, and three more with each cooperating teacher, responsible for the subject Knowledge of Cultural and Social Environment in the practice class). During the intensive practice placement (in February), the preservice teachers gave a didactic unit within this area. The topics were «The Catalan counties» in 4th grade, «The textile industry» also in 4th grade, and «The European Union» in 6th grade. The practice final reports explained and analyzed the preparation, carrying out and assessment of these sessions, some of which were directly observed by the researcher. The written reports are responsible for the greatest amount of information collected, including initial assessment activities, different exercises carried out in the classroom, individual assignments, exams, practice reports… In the final interpretation of information obtained for each case, six variables of the training process were analyzed: the preservice teachers themselves, the cooperating teachers, the groups of Primary pupils, the contexts of practice (availability of space, time, material...), the practice tutor of the Faculty, and the teacher of the Social Studies Methods course. The conclusions show some coincidences in the difficulties the three preservice teachers found when reasoning and changing their concepts and practice to teach social studies. The thesis points at the modifications that should be introduced in the course syllabus, but also in the Practicum and in the overall current Teacher Training curriculum, so that undergraduates and teachers have more favorable conditions to build a more innovating Social Studies teaching model together and more significantly

Temperature-Dependent Sex Determination in Fish Revisited: Prevalence, a Single Sex Ratio Response Pattern, and Possible Effects of Climate Change

11 pages, 5 figures, 2 tables.-- PMID: 18665231 [PubMed].-- Supporting information available: Supplementary Table "Field and laboratory data used for the assessment of the presence of temperature-dependent sex determination in gonochoristic fish" and list of references[Background] In gonochoristic vertebrates, sex determination mechanisms can be classified as genotypic (GSD) or temperature-dependent (TSD). Some cases of TSD in fish have been questioned, but the prevalent view is that TSD is very common in this group of animals, with three different response patterns to temperature.[Methodology/Principal Findings] We analyzed field and laboratory data for the 59 fish species where TSD has been explicitly or implicitly claimed so far. For each species, we compiled data on the presence or absence of sex chromosomes and determined if the sex ratio response was obtained within temperatures that the species experiences in the wild. If so, we studied whether this response was statistically significant. We found evidence that many cases of observed sex ratio shifts in response to temperature reveal thermal alterations of an otherwise predominately GSD mechanism rather than the presence of TSD. We also show that in those fish species that actually have TSD, sex ratio response to increasing temperatures invariably results in highly male-biased sex ratios, and that even small changes of just 1–2°C can significantly alter the sex ratio from 1:1 (males:females) up to 3:1 in both freshwater and marine species.[Conclusions/Significance] We demonstrate that TSD in fish is far less widespread than currently believed, suggesting that TSD is clearly the exception in fish sex determination. Further, species with TSD exhibit only one general sex ratio response pattern to temperature. However, the viability of some fish populations with TSD can be compromised through alterations in their sex ratios as a response to temperature fluctuations of the magnitude predicted by climate changeWork supported by a Spanish Ministry of Education and Science grant ("Sexratio") to F.P. N.O.A. was supported by a scholarship from the aquaculture network (XRAq) from the Government of CataloniaPeer reviewe

Temperature Effects on Global DNA Methylation and Gene Expression During Larval development in the European Sea Bass

1 page• Fish represent good animal models for the purposes of identifying persistent epigenetic marks which arise from different early developmental environments and which correlate with relevant biological processes later in life. • In sexually differentiated one-year-old European sea bass (Dicentrarchus labrax), the methylation levels of the promoter of gonadal aromatase (cyp19a), which converts androgens into estrogens, have been shown to increase in females after exposure of larvae to high temperature during the thermosensitive period (TSP) [1]. • The goal of this study was to determine whether temperature treatments during different time intervals within the TSP are able to alter the genome-wide patterns of DNA methylation and the expression of specific genes.Supported by grant AGL2010-15939 (“Epigen-Aqua”) to FPPeer Reviewe

Towards a Transnational Civil Society : Actors and Concepts in Europe from the Late Eighteenth to the Twentieth Century

Since late eighteenth-century Enlightenment, the concept of civil society has increasingly assumed a transnational dimension that has given rise to political debates and attracted scholarly interest. This paper provides a research report and a historical overview of the emergence and transformation of civil society organizations that have transcended national borders and cultural boundaries, especially International Non-Governmental Organizations. Based on deliberations about the definition and conceptualization of ‘transnational civil society’, the investigation concentrates on the abolitionists, the workers’ organizations as well as on peace and on women’s movements. The authors suggest that further historical studies of transnational civil society should relate its groups and activists to specific contexts and conditions. They also argue that further research should pay particular attention to the actors of transnational civil society, their performance and representations. Overall, static conceptions of transnational civil society have ignored its flexibility and changeability over the course of the last two centuries.Seit der Aufklärung im späten 18. Jahrhundert hat der Begriff Zivilgesellschaft eine zunehmend transnationale Dimension erreicht, die insbesondere politische Diskussionen und wissenschaftliches Interesse auslöste. Das vorliegende Diskussionspapier lässt sich als Forschungsbericht verstehen, der einen historischen Überblick über Auftreten und Transformation zivilgesellschaftlicher Organisationen gibt, die insbesondere national und kulturell grenzüberschreitend institutionalisiert sind, wie beispielsweise internationale Nichtregierungsorganisationen. Auf der Grundlage einer sorgfältigen Analyse von Definition und Konzeption ‚transnationaler Zivilgesellschaft’, konzentriert sich die Untersuchung vor allem auf die Gegner der Todesstrafe, aber auch Gewerkschaften sowie Friedens- und Frauenbewegungen. Beide Autoren plädieren für eine Auseinandersetzung mit der Thematik aus historischer Perspektive, um insbesondere bestimmte Gruppen und Aktivisten in direkten Bezug zu ihrem historischen Kontext und Vorbedingungen zu stellen. Darüber hinaus heben sie hervor, dass daran anknüpfende Studien gerade den Akteuren, ihrem Auftreten und ihrer Präsentation gewidmet werden sollen. Im Gesamtzusammenhang lässt sich festhalten, dass die bisher eher statisch geprägten Untersuchungen zum Forschungsschwerpunkt ‚transnationale Zivilgesellschaft’ insbesondere die Flexibilität und Unbeständigkeit derselbigen in den letzten beiden Jahrhunderten nicht berücksichtigten

Control neuroendocrí de l'inici de la maduresa sexual en els vertebrats mitjançant la kisspeptina i el seu receptor, amb especial èmfasi pel que fa a la situació en els peixos teleostis

El recent descobriment de la kisspeptina (producte del gen KISS1), conjuntament amb el seu receptor (producte del gen KISS1R), i de la seva relació amb el control de l'inici de la maduresa sexual en tots els vertebrats, ha estat descrit com una de les troballes més rellevants de la biologia reproductiva en els últims anys. La kisspeptina té un efecte directe sobre l'hormona alliberadora de gonadotrofines, la qual desencadena una cascada hormonal que finalment acaba a les gònades amb la secreció dels esteroides sexuals, els quals provoquen la consegüent maduració de l'individu. En aquest treball s'explica el descobriment dels gens KISS1 i KISS1R, l'estructura d'aquests gens i dels seus productes proteics, i es fa referència als mecanismes endocrins responsables tant de la regulació endògena com dels possibles factors externs que afecten el sistema kisspeptina-KISS1R. També, i amb especial èmfasi en els peixos teleostis, es discuteixen les possibles causes de les diferències i similituds trobades en l'expressió cerebral del sistema kisspeptina-KISS1R. Finalment, s'avaluen les perspectives futures en el camp del control de la reproducció mitjançant la manipulació del sistema kisspeptina-KISS1R.The discovery of kisspeptin (the product of the KISS1 gene) together with its receptor (product of the KISS1R gene), and the relationship with the control of the onset of puberty in all vertebrates has been described as one the most important findings in reproductive biology in the last years. Kisspeptin stimulates gonadotrophin-releasing hormone (GnRH), initiating the hormonal cascade which ends in the gonads with the secretion of the sex steroids which, in turn, drive sexual maturation. This paper describes the origin and discovery of the KISS1 and KISS1R genes, the structure of these genes as well as their protein products. The endocrine mechanisms and the exogenous factors affecting the kisspeptin- KISS1R complex are also discussed. Finally, we describe the multiple functions in relationship with this system in all vertebrates and discuss the differences and similarities regarding the neural expression of kisspeptin-KISS1R complex in several teleost fishes. Finally, the future perspectives in the field of the control reproduction by the manipulation of the kisspeptin-KISS1R complex are discussed

Cloning and sequence analysis of a vasa homolog in the European sea bass (Dicentrarchus labrax): Tissue distribution and mRNA expression levels during early development and sex differentiation

12 pages, 7 figuresVasa is a protein expressed mainly in germ cells and conserved across taxa. However, sex-related differences and environmental influences on vasa expression have not been documented. This study characterized the cDNA of a vasa homolog in the European sea bass, Dicentrarchuslabrax (sb-vasa), a gonochoristic fish with temperature influences on gonadogenesis. The 1911 bp open reading frame predicted a 637-amino acid protein with the eight conserved domains typical of Vasa proteins. Comparisons of the deduced amino acid sequence with those of other vertebrates and invertebrates revealed the highest homology (68–85%) with those of other teleosts. An updated tree with the full-length sequences for Vasa proteins in 66 species belonging to six different phyla was constructed, establishing the evolutionary relationships of Vasa amino acid sequences. European sea bass vasa was highly expressed in gonads with little or no expression in other tissues. Real time RT-PCR quantification of the temporal expression of sb-vasa from early development throughout sex differentiation showed that mRNA levels were high in unfertilized eggs, decreased during larval development and increased again during the period of germ cell proliferation. Rearing of fish at high temperature resulted in further increased sb-vasa levels, most likely reflecting temperature effects on both somatic and gonadal growth. Differences in expression were also found well before sex differentiation and persisted until the end of the first year, with higher levels present in females. These differences in expression demonstrate the implication of vasa during the initial stages of fish sex differentiation and gametogenesis and suggest that, through its helicase activity, it might be implicated in the translational regulation of mRNAs involved in the specification and differentiation of gonadal-specific cell typesThis work was supported by the EU grant PROBASS (Q5RS-2000-31365) to F.P and C.C.M. Research at the lab of F.P. is partially funded by project Consolider ‘‘Aquagenomics” CDS2007-0002. M. Blázquez was supported by a postdoctoral contract from the EU and a Ramón y Cajal contract from the Spanish Ministry of Science and TechnologyPeer reviewe

Aplicació de la biotecnologia a l'aqüicultura

L'aqüicultura és cada cop més important en el proveïment de proteïna d'origen aquàtic en un món en què la pesca ha tocat sostre en el nombre de captures anuals a causa de la sobreexplotació dels oceans. A més, hi ha un augment continuat tant de la població humana com del requeriment d'aquesta proteïna d'aliments d'origen marí. En aquest context, l'aqüicultura esdevé un procés de producció d'aliments fortament tecnificat i industrialitzat. La contribució de la biotecnologia a aquest sector de l'alimentació és encara incipient però molt prometedora. Aquí es repassen les aplicacions de la biotecnologia a l'aqüicultura, algunes ja en explotació, altres encara en fase experimental. Aquestes aplicacions inclouen el control de la reproducció —selecció del sexe, producció de poliploides i línies clonals i xenotrasplantaments de la línia germinal—; el control del creixement —producció d'animals transgènics de ràpid creixement o adaptats a ambients extrems—; la prevenció de malalties —vacunes de DNA i detecció de la presència de patògens—; i el proveïment d'unes condicions de cria òptimes –monitorització de l'estat d'estrès i de les variables ambientals. Aquestes aplicacions han d'assegurar el benestar dels animals i la qualitat del producte que s'espera, tot en un context de producció sostenible i respectuosa amb el medi ambient.Aquaculture is increasingly becoming more relevant for the supply of animal protein of aquatic origin in a world where capture fisheries has reached an all-time maximum in annual landings due to overfishing of the oceans. Furthermore, there is a sustained increase in both the human population and the requirement of this population for food supplies of aquatic origin. In this context, aquaculture is becoming a food sector increasingly technified and industrialized. The contribution of biotechnology to aquaculture is still incipient but it holds a great deal of promise. Here, several applications of biotechnology to aquaculture are reviewed, some of them already being applied commercially, others still in the development phase. These applications include the control of reproduction –sex control, production of polyploids and clonal lines, and xenotransplantation of the germinal line; growth control—production of transgenics for superior growth or adapted to extreme environments—; disease prevention—DNA vaccines and pathogen detection—; and the providing of optimal growth conditions—stress and environment monitoring. These applications must ensure the welfare of the farmed animals and the quality products that one expects from aquaculture, all in a context of sustainable production respectful with the environment

Heat-induced masculinization in domesticated zebrafish is family-specific and yields a set of different gonadal transcriptomes

Understanding environmental influences on sex ratios is important for the study of the evolution of sex-determining mechanisms and for evaluating the effects of global warming and chemical pollution. Fishes exhibit sexual plasticity, but the underlying mechanisms of environmental effects on their reproduction are unclear even in the well-established teleost research model, the zebrafish. Here we established the conditions to study the effects of elevated temperature on zebrafish sex. We showed that sex ratio response to elevated temperature is family-specific and typically leads to masculinization (female-to-male sex reversal), resulting in neomales. These results uncovered genotype-by-environment interactions that support a polygenic sex determination system in domesticated (laboratory) zebrafish. We found that some heat-treated fish had gene expression profiles similar to untreated controls of the same sex, indicating that they were resistant to thermal effects. Further, most neomales had gonadal transcriptomes similar to that of regular males. Strikingly, we discovered heat-treated females that displayed a normal ovarian phenotype but with a “male-like” gonadal transcriptome. Such major transcriptomic reprogramming with preserved organ structure has never been reported. Juveniles were also found to have a male-like transcriptome shortly after exposure to heat. These findings were validated by analyzing the expression of genes and signaling pathways associated with sex differentiation. Our results revealed a lasting thermal effect on zebrafish gonads, suggesting new avenues for detection of functional consequences of elevated temperature in natural fish populations in a global warming scenario